Humanitarian groups operating rescue ships off the coast of Libya picked up more than 700 migrants out of seven flimsy and overcrowded boats on Wednesday, Italy's coast guard said.

The Phoenix rescue ship, operated by the Malta-based non-governmental organization MOAS, rescued more than 300 people from three boats in international waters off the coast of the Libyan city of Sabratha.

The Aquarius, operated by SOS Mediterranee and Doctors without Borders, went to the aid of four rubber boats, a coast guard spokesman said. Italy's coast guard coordinated the rescues.

Migrants arriving in Italy on boats from North Africa are up some 30 percent so far this year, according to official data released last week.

Some 600 people have died trying to reach Italy this year, said the International Organization for Migration. No bodies were found on Wednesday, the coast guard said.